1. Field of the Invention
The present invention relates to a multilayer filter.
2. Related Background Art
In recent years, noise filters having surge functions have been used in various electronic equipment as components to alleviate EMC. In Patent Document 1 (See for Japanese Patent Publication No. 2626143), a multilayer composite electronic component is disclosed in which a magnetic layer, in which a prescribed conductor pattern is formed internally, and a varistor layer, in which a prescribed conductor pattern is formed internally, are layered, and the magnetic layer and varistor layer are electrically connected by means of a through-hole.
However, in the above Patent Document 1 the magnetic layer and varistor layer are integrally sintered, and material components comprising the respective layers may diffuse into the other layer through the interface between the magnetic layer and the varistor layer. When diffusion of these material components occurs, the characteristics of the layers in which diffusion occurs are affected, and there are concerns that noise filter functions may be degraded. In the above Patent Document 1, an Ni—Cu—Zn system ferrite is used in the magnetic layer, but studies by these inventors have revealed that when a magnetic layer comprising such a material is integrally sintered with a varistor layer, the Cu component in the magnetic layer diffuses into the varistor layer, permeating into the region which manifests the varistor characteristics, degradation of varistor functions, and in particular of the attenuation characteristic, occurs.